Allow a WordPress custom post type to select another post type as a parent.

wp-post-type-parent-of-another-post-type.php

// Source: http://janina.tumblr.com/post/3588081423/post-parent-different-type
// Modified to be more generic

add_action('admin_menu', function() { 
  remove_meta_box( 'pageparentdiv', 'post-type', 'normal'); 
});

add_action('add_meta_boxes', function() { 
    add_meta_box( 'post-type-parent', 'Section', 'post_type_attributes_meta_box', 'post-type', 'side', 'high');
});

function post_type_attributes_meta_box($post) {
    $post_type_object = get_post_type_object($post->post_type);
    
    if ( $post_type_object->hierarchical ) {
        $pages = wp_dropdown_pages(array('post_type' => 'post-type', 'selected' => $post->post_parent, 'name' => 'parent_id', 'show_option_none' => __('(no parent)'), 'sort_column'=> 'menu_order, post_title', 'echo' => 0));
        if ( ! empty($pages) ) {
            echo $pages;
        } // end empty pages check
    } // end hierarchical check.
}

Hi jwondrusch , not working url from CPT Child.

site.com/parent/child --> 404 .

you had that problem? Thanks